2.8: How to assign a Procedural "wood" texture(for example) i just made to a material
Uhh... you raise an excellent point, actually.

The short answer is:


Ensure the Viewport Shading type in the top right is set to Look Dev or Rendered, not Solid.
In the Shading workspace or any Shader Editor, edit your Material, setting the Base Colour type to use a Wave Texture Node. There is no 'Wood'. It's kinda weird.


So... creating that Wood Texture on the right-side Textures context doesn't really do anything - it's showing your Brush and Brush Mask textures. Procedural textures aren't really 'stored' how you may expect.

The Nodes you would use to get the same procedural effects have completely inconsistent names with the list of texture types on that Texture tab.
I haven't looked into this, but there's probably a developer discussion about sorting this all out, because until I tried answering your question I hadn't really realised what an utter mess that all is.

Here's a shader editor showing all the Texture node types available... beside the list of texture names on that tab. I'm slightly baffled, to be honest.